The present invention is directed generally to tape measures, and more particularly to power return tape measures and/or housings therefor.
Modem tape measures (or xe2x80x9ctape rulesxe2x80x9d) typically include a coiled tape that is spring-biased towards a retracted position. A housing generally surrounds and protects the tape and a retraction spring and includes an opening through which a distal end of the tape extends. Typically, the tape measure housing consists of two housing halves that are joined together by one or more screws. In addition, one of the housing halves typically includes an inwardly pointing integral post that provides an anchoring point for one end of the retraction spring. During assembly, the reel is placed over the post with the retraction spring engaged by the post, and the other housing half is then joined to the first housing half with blade winding reel captured therebetween. During use, the distal end of the tape is pulled away from the housing; when released, the spring pulls the tape back into the housing so that the tape returns to the retracted position. The retracted tape is typically wound on the reel that is in turn rotatably supported by the housing.
One important consideration when designing commercially available tape measures is that the tape measure should be able to function even after being repeatedly dropped, as frequently occurs on a construction site. Dropping the tape measure subjects the tape measure housing to substantial shock loadings that tend to distort the housing halves. When the housing halves are distorted, the internal post may become dislodged from its desired position, leading to uneven loading on the post, and ultimately failure. Indeed, it is believed that one of the major causes of tape measure failure is breakage of the post, which un-anchors the retraction spring inside the housing, thereby damaging the return mechanism, and possibly the entire inner chamber of the housing, typically rendering the tape measure unusable.
Another consideration in designing tape measure housings is the torsional loading placed on the post by the retraction spring. As tape blade lengths increase, more powerful springs are required, which leads to more torsional loading on the posts. Because the posts and housing halves are typically made from injection molded plastic materials, the material strength of the posts have not always been capable of withstanding these increased torsional loadings on the post.
Accordingly, there remains a need for improved tape measure housing designs, particularly those that have a more robust post design, an preferably designs that address one or more of the problems outlined above.
The present invention is directed to a tape measure housing, a tape measure incorporating the housing, and/or a method of assembling a tape measure, each of which use a post joined to at least one sidewall of the housing.
In one embodiment, the tape measure housing comprises a main case having first and second sidewalls and a peripheral wall extending between the sidewalls. A post is disposed between the first and second sidewalls. The post has an elongate column portion disposed along an axis and a base portion. The base portion includes a plurality of ribs extending generally normal to the axis. The column portion includes a slot and optionally a terminal hole. The second sidewall may include a boss having a recess configured to accept at least the ribs of the post. Ideally, the material forming the boss interstitially interengages with the ribs of the post. The anchoring portion of the post may optionally include a flange extending generally normal to the axis, with the flange having a non-circular shape and the recess configured to accept the flange. The first sidewall may include another boss having a recess configured to accept a terminal portion of the column portion of the post. The post may be made from metal. Preferably, a fastener (e.g., screw) extends through the first sidewall and mates to the terminal hole of the post. More preferably, another fastener also extends through the second sidewall and mates to the base portion of the post.
In another embodiment, a method of assembling a tape measure includes providing a main case having first and second sidewalls and a peripheral wall extending between the sidewalls; disposing a post between the first and second sidewalls, the post having an elongate column portion disposed along an axis and a base portion, the base portion including a plurality of ribs extending generally normal to the axis, the column portion including a slot and optionally having a terminal hole; rotatably supporting a reel within the main case; providing a tape blade convolutionally wound on the reel; optionally mating a fastener to the post through the first sidewall; optionally mating another fastener to the post through the second sidewall; and operatively connecting a spring to the slot and to the tape blade, the spring biasing the tape blade for retraction into the main case. Providing the main case having first and second sidewalls and the peripheral wall extending between the sidewalls may comprise providing distinct first and second case portions, wherein the first case portion includes the first sidewall and the second case portion includes the second sidewall.
In still another embodiment, a tape measure may use the tape measure housing and/or method of assembly described above.